1) Field of the Invention
The invention herein relates to mechanical rotation safety protection mechanisms, specifically an end surface gear-type overload protection device for manually operated hoists.
2) Description of the Prior Art
Conventional manually operated hoist structures are categorized into two types: hand crank type or hand chain type, wherein the “hand crank type” hoist, as shown in FIG. 13, is comprised of a load pulley wheel 2 ensconced along with a bearing device between a pair of side plates 1 as well as an operating drive component 3 disposed at the outer lateral extent of the side plates 1 that drives a transmission shaft 4 accompanied by a gear reduction mechanism 5 at its axial lateral extent, said drive component 3 consisting of a hand crank arm 3a having a single-direction drive ratchet wheel 3b, a pawl 3c, and a pawl spring 3d such that the rapid operation of the hand crank arm 3a turns the drive shaft 4 which pulls over said load pulley wheel 2 a chain 6 connected to a hoisting hook 6a coupled to a heavy object; the “hand pull type” hoist, as shown in FIG. 14, generally consists of, in common with the hand crank type structure, side plates 1, a load pulley wheel 2, a transmission shaft 4, a gear reduction mechanism 5, a chain 6 connected to a hoisting hook 6a, and other necessary drive components, the difference is that the power input section drive component 7 is instead a hand pull chain 7a and at its lateral axial aspect has a direction alternating ratchet wheel 8 and a pawl 8a which replaces the drive component 3 of said hand crank type structure, the hand pull type variant utilizing the hand pull wheel 7 over which is diametrically disposed a hand pull chain 7b to draw and thereby operate, at the other end of the transmission shaft 4, a load pulley wheel 2 and its chain 6 connected to a hoisting hook 6a coupled to a heavy object; since the hand crank type and the hand pull type structures are uncomplicated, portable, and convenient, they are widely used for loading cargo, unloading cargo, and strapping cargo. As such, in keeping with their operating characteristics, they are often utilized in an overloaded state and there is no limiting overload setting which, especially when lifting and strapping loads, tends to concentrate hoisting load stress at certain points, the hoisting hook 6a easily subjecting the chain 6, brake, and other components of the hoist to excessive wear, while also easily damaging goods and causing industrial accidents wherein operating personnel suffer injury.